when ever I enter a room and there is smoke or dust my computer lags and slows
Check the Call of Duty website to find out the optimal settings for playing Call of Duty with Windows 7. Make sure your settings are set to the optimal settings. If they are and you are still having problems, change the resolution of the game and see if that helps.
Still need help? Check out these tips on fixing game performance - http://windows.microsoft.com/en-US/windows7/Fixing-game-performance-problems
Microsoft Windows Outreach